1. Field of the Invention
This invention relates to punch press dies, and more particularly to a punch press die assembly capable of selectively changing the positions of punching holes in a number of different patterns.
2. Description of the Prior Art
The means which are generally resorted to for forming perforations in a steel plate or other sheetlike material include the boring by drills and the punching by presses.
In the boring operation by a drill, there is a possibility of the operator getting hurt due to the necessity for manually removing the chips which remain on the bored work. Besides, since there is a possibility of failure which might have been caused by abrasive wear of a drilling tool or by a damage due to fluttering of the drilling tool, it is necessitated to confirm whether the holes have been bored or not after each boring operation, which results in requiring superfluous operation. Another problem involved in the drilling operation is the difficulty of drilling holes in close positions for the necessity of securing spaces for holding the drills. In such a case, there have to be provided a plural number of drilling machines, which naturally increases the equipment cost.
On the other hand, the punch presses which are capable of forming a greater number of holes by a single downward punching motion of the upper die have advantages over the drills in terms of savings in time and cost, but the punch presses have a problem that the punching positions are invariably determined by the positions of the punches which are mounted on the upper die. Namely, it has been difficult to change the positions of holes to be punched in each punching operation or to punch holes selectively.